I used the data from Feb, 2004 and Feb, 2009 to create the following graph. It’s visually clear that in the past 5 years, users are increasing the number of words in their search queries. In 2004, more than 50% of the searches had only 1 or 2 words. In 2009, the trend has reversed. Now more than 50% of searches contain 3 or more words.  

While it’s great to rank for 1 or 2 word search phrases, in order to maximize impact, your seo efforts need to include a variety of phrases that contain 3 or more words.